TRANSACTIONS OF THE INSTITUTE OF MOLECULAR BIOLOGY AND BIOTECHNOLOGIES
Institute of Molecular Biology, Ministry of Science and Education of the Republic of Azerbaijan
TRANSACTIONS OF THE INSTITUTE OF MOLECULAR BIOLOGY AND BIOTECHNOLOGIES
Institute of Molecular Biology, Ministry of Science and Education of the Republic of Azerbaijan
*For correspondence: tjussifo@ucla.edu, talehy671@gmail.com
Fidan Qudretova: https://orcid.org/0009-0005-9597-5066 Nicoletta Savalli: https://orcid.org/0000-0001-7267-9655 Enrique Balderas: https://orcid.org/0000-0001-8780-9272 Sevda Mahmudova: https://orcid.org/0000-0001-8207-0544 Aysel Aliyeva : https://orcid.org/0009-0005-2826-0335 Gunay Aliyeva: https://orcid.org/0009-0002-1183-2593 Taleh Yusifov: https://orcid.org/0009-0002-8486-5695
Our recent studies have identified a novel module in the BK channel reminiscent of the cytochrome c domains of hemoproteins. This feature may explain the distinctive physiological functions of these widespread ion channels. To further elucidate the structural and functional implications, we investigated how BK channel activity responds to reactive oxygen species (ROS), with a particular focus on hydrogen peroxide (H 2 O 2 ). We demonstrated that the human BK channel possesses enzymatic activity that efficiently cleaves H 2 O 2 . To elucidate this novel catalytic activity in a physiological context, we are conducting experiments using a biochemical assay of the human BK channel and studies in human embryonic kidney (HEK293) cell lines. Our experiments using ABTS and Amplex Red assay showed that the C-terminal protein, isolated from the soluble and incorporated fractions, catalyzes H 2 O 2 cleavage unless heme is added, at which point the protein exhibits catalytic activity. Our experiments using the intact human BK channel revealed a significant protective effect of wild-type BK channels against oxidative stress by enhancing HEK cell tolerance to (H 2 O 2 ): at 200 μM H 2 O 2 , 37%±6% of cells expressing only YFP survived. In contrast, 60%±4% of HEK cells expressing wild- type BK channels were viable. However, a mutant with a disrupted heme-binding site (C615S H616R) did not provide protection. We demonstrated that the BK channel exhibits modulatory activity at the H 2 O 2 level. Most importantly, this novel enzymatic activity of BK likely has physiological significance: non-conducting BK channels with intact heme-binding properties enhance cell survival against oxidative stress.
The authors would like to express their deep gratitude to Doctors of Biological Science Karim Gasimov and Professor Oktay Gasimov for their incredible support in conducting the study and for their contributions to the manuscript.
Taleh Yusifov: Conceptualization, Writing – review & editing; Fidan Gudratova: Data curation, Visualization, Software; Enrique Balderas Data curation; Nicoletta Savalli: Data curation, Formal analysis; Sevda Mahmudova: Visualization, Software; Aysel Aliyeva: Visualization; Gunay Aliyeva: Software
Not applicable.
No funding was received for this study.
None.
R., Friedrich M., Plass W. et al. (2013) Heme impairs the ball-and-chain inactivation of potassium channels. Proceedings of the National Academy of Sciences of the United States of America, 110(42), E4036–E4044.
Sahoo N., Yang K., Coburger I., Bernert A., Swain S.M., Gessner G. et al. (2022) Intracellular hemin is a potent inhibitor of the voltage-gated potassium channel Kv10.1. Sci. Rep., 12(1): 14645.
Sancho M., Kyle B.D., Sancho M., Kyle B.D. (2021). The Large-conductance, calcium-activated potassium channel: A big key regulator of cell physiology. Frontiers in Physiology, 12: 750615.
Soladogun A.S., Zhang L. (2024) The neural palette of Heme: Altered Heme homeostasis underlies defective neurotransmission, increased oxidative stress, and disease pathogenesis. Antioxidants, 13(12):1441.
Tang X.D., Xu R., Reynolds M.F., Garcia M.L., Heinemann S.H., Hoshi T. (2003) Haem can bind to and inhibit mammalian calcium-dependent Slo1 BK channels. Nature, 425(6957): 531–535.
Walewska A., Szewczyk A., Koprowski P. (2022) External Hemin as an inhibitor of mitochondrial large-conductance calcium-activated potassium channel activity. Int. J. Mol. Sci., 23(21):13391.
Wang S., Publicover S., Gu Y. (2009) An oxygen-sensitive mechanism in regulation of epithelial sodium channel. Proceedings of the National Academy of Sciences USA, 106(8):2957–2962.
Yusifov T., Aliyeva A., Gudratova F., ... Aliyeva N. (2026) Ion channels and regulatory signals of heme. European Journal of Biology, 85(1): 5765; doi: 10.26650/EurJBiol.2026.1756794
Yusifov T., Qudretova F., Aliyeva A. (2025) Cytochrome C-like domain within the human BK channel. InAI-assisted tools were used only for language translation, grammatical editing, and reference formatting.
Belikova N.A., Vladimirov Y.A., Osipov A.N., Kapralov A.A., Tyurin V.A., Potapovich M.V. et al. (2006) Peroxidase activity and structural transitions of cytochrome c bound to cardiolipin-containing membranes. Biochemistry, 45(15): 4998-5009.
Belikova N.A., Jiang J., Tyurina Y.Y., Zhao Q., Epperly M.W., Greenberger J. et al. (2007) Cardiolipin-specific peroxidase reactions of cytochrome c in mitochondria during irradiation-induced apoptosis. International Journal of Radiation Oncology, Biology, Physics, 69(1): 176–186.
Bertini I., Cavallaro G., Rosato A. (2006) Cytochrome c: Occurrence and functions. Chem. Rev., 106(1): 90–115.
Burton M.J., Cresser-Brown J., Thomas M., Portolano N., Basran J., Freeman S.L. et al. (2020) Discovery of a heme-binding domain in a neuronal voltage-gated potassium channel. Journal of Biological Chemistry, 295(38):13277–13286.
Burton M.J., Kapetanaki S.M., Chernova T., Jamieson A.G., Dorlet P., Santolini J. et al. (2016) A heme-binding domain controls regulation of ATP-dependent potassium channels. Proceedings of the National Academy of Sciences USA, 113(14):3785–90.
Coburger I., Yang K., Bernert A., Wiesel E., Sahoo N., Swain S.M. et al. (2020) Impact of intracellular hemin on N-type inactivation of voltage-gated K+ channels. Pflugers Arch., 472(5): 551-560.
Coletta M., Bolognesi M., Ascenzi P. (2024) Heme is pivotal for life. J. Inorg. Biochem., 250: 112423.
Cui J. (2021). BK Channel Gating Mechanisms: Progresses Toward a Better Understanding of Variants Linked Neurological Diseases. Frontiers in physiology, 12: 762175.
Dutt S., Hamza I., Bartnikas T.B. (2022) Molecular mechanisms of iron and heme metabolism. Annu. Rev. Nutr., 42(1):311–35.
Echeverría F., Gonzalez-Sanabria N., Alvarado-Sanchez R., Fernández M., Castillo K., Latorre R. (2024) Large conductance voltage-and calcium-activated K+ (BK) channel in health and disease. Frontiers in pharmacology, 15, 1373507.
Espinosa-Cantú A., Cruz-Bonilla E., Noda-Garcia L., DeLuna A. (2020) Multiple forms of multifunctional proteins in health and disease. Front. Cell Dev. Biol., 8: 451; doi: 10.3389/fcell.2020.00451.
Flores C.L., Gancedo C. (2011) Unraveling moonlighting functions with yeasts. IUBMB Life, 63(7):457-62. doi: 10.1002/iub.454.
Giangiacomo K.M., Garcia M.L., McManus O.B. (1992) Mechanism of iberiotoxin block of the large-conductance calcium-activated potassium channel from bovine aortic smooth muscle. Biochemistry, 31(29): 6719.
Gudratova F., Aliyeva A., Mahmudova S., Gasimov K., Yusifov T. (2025) ABTS oxidation reaction as a model of cytochrome c-driven electron transfer. The Ukrainian Biochemical Journal, 97(4): 43-51.
Gudratova F., Savalli N., Aliyeva A., ...Yusifov T. (2026). Heme signaling through the cytochrome c-like domain of the human BK channel. Biochimica et Biophysica Acta, Biomembranes, 1868(3): 184533; doi: 10.1016/j.bbamem.2026.184533
Horrigan F.T., Heinemann S.H., Hoshi T. (2005) Heme regulates allosteric activation of the Slo1 BK channel. J. Gen. Physiol., 126(1): 7–21.
Hoshi T., Heinemann S.H. (2016). Modulation of BK channels by small endogenous molecules & pharmaceutical channel openers. International review of neurobiology, 128: 193–237.
Hoshi T., Pantazis A., Olcese R. (2013) Transduction of voltage and Ca2+ signals by Slo1 BK channels. Physiology, 28(3): 172–89.
Huang Y., Kumar S., Lee J., Lu W., Du J. (2024) Coupling enzymatic activity and gating in an ancient TRPM chanzyme and its molecular evolution. Nat. Struct. Mol. Biol., 31(10):1509-1521; doi: 10.1038/s41594-024-01316-4.
Javaherian A.D., Yusifov T., Pantazis A., Franklin S., Gandhi C.S., Olcese R. (2011) Metal-driven operation of the human large-conductance voltage- and Ca2+-dependent potassium channel (BK) gating ring apparatus. J. Biol. Chem., 286(23):20701-20709; doi: 10.1074/jbc.M111.235234.
Kagan V.E., Tyurin V.A., Jiang J., Tyurina Y.Y., Ritov V.B., Amoscato A.A. et al. (2005) Cytochrome c acts as a cardiolipin oxygenase required for release of proapoptotic factors. Nat. Chem. Biol., 1(4): 223–232.
Kelkar Y.D., Ochman H. (2013) Genome reduction promotes increase in protein functional complexity in bacteria. Genetics, 193(1):303-307. doi: 10.1534/genetics.112.145656.
Pantazis, A., & Olcese, R. (2016). Biophysics of BK Channel Gating. International Review of Neurobiology, 128: 1-49.
Sahoo N., Goradia N., Ohlenschläger O., Schönherrt. J. Mol. Sci., 26(15): 7053.
Received: April 01, 2026; Reviewed: May 21, 2026; Accepted: June 01, 2026
DOI:
https://doi.org/10.62088/timbb/10.1.1Keywords:
MaxiK, Slo1, heme regulatory motif, electronic absorption spectroscopy, heme sensor, ABTS oxidation, oxidative stress, ROS
Gudratova F., Savalli N., Balderas E., Mahmudova S., Aliyeva A., Aliyeva G., Yusifov T. (2026). The human large-conductance, calcium-activated potassium channel covers cell resistance to oxidative damage. TIMBB, 10 (1), 3-11.